Re: [PATCH 0/8] Suspend block api (version 6)

From: Matthew Garrett
Date: Mon May 03 2010 - 20:44:11 EST


On Mon, May 03, 2010 at 04:37:22PM -0700, Kevin Hilman wrote:

> Please forgive the ignorance of ACPI (in embedded, we thankfully live
> in magical world without ACPI) but doesn't that already happen with
> CPUidle and C-states? I think of CPUidle as basically runtime PM for
> the CPU. IOW, runtime PM manages the devices, CPUidle manages the CPU
> (via C-states), resulting in dynaimc PM for the entire system. What
> am I missing?

ACPI doesn't provide any functionality for cutting power to most devices
other than shifting into full system suspend. The number of wakeup
events available to us on a given machine is usually small and the
wakeup latency large, so it's not terribly practical to do this
transparently on most hardware.

--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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